1. Field of the Invention
The present invention relates to a fluid compressor for compressing a refrigerant gas, for example, in a refrigerating cycle.
2. Description of the Related Art
There are known various types of compressors, for example, reciprocation type, rotary type, etc. In these compressors, however, the structure of a driving unit, such as a crank shaft for transmitting torque to a compressor unit, and the structure of the compressor unit are complex, and the number of parts is large.
In order to increase the compression efficiency of the compressor, a check valve must be provided on the discharge side. In this case, since a pressure difference between both sides of the check valve is very large, the possibility of gas leakage from the check valve is high. As a result, the compression efficiency is decreased.
In order to solve this problem, high precision is required for the respective parts of the compressor and for the assembly thereof, resulting in an increase in manufacturing cost.
U.S. Pat. No. 4,872,820 discloses a fluid compressor wherein a rod is eccentrically disposed within a cylinder, a spiral groove is formed in the outer peripheral surface of the rod, and a spiral blade is slidably fitted in the spiral groove.
The cylinder and the rod move relative to each other, and a fluid is compressed in the axial direction of the cylinder while being transferred from the suction side to the discharge side of the cylinder. The blade is inclined such that an outer peripheral end portion thereof is directed towards the discharge side.
U.S. Pat. No. 4,871,304 discloses a fluid compressor having substantially the same structure as the compressor of U.S. Pat. No. 4,872,820, wherein the pitch of the blade decreases towards the discharge side and a high pressure is created in a bottom space of a spiral groove, in which the blade is fitted, through a pressure introducing path.
U.S. Pat. No. 4,875,842 discloses a fluid compressor having substantially the same structure as the compressor of U.S. Pat. No. 4,872,820, wherein one of bearings for supporting both ends of a cylinder is supported unrotatably but movable in the axial and radial directions of the cylinder, and that the angle of the spiral groove is specified.
In each of the above conventional compressors, the sealing of the blade in the spiral groove is not perfectly maintained, and it is possible that the compressed fluid may leak between working chambers which are adjacent to each other via the blade, resulting in a decrease in compression efficiency.